Apparatus for casting directionally solidified articles



United States Patent [72] inventor Charles M. Phipps, Jr. [56] References Cited t l l ui Connecticut UNITED STATES PATENTS g Q J' l g 3,234,609 2/1966 Madono.... l64/127X l 3,366,362 1/1968 Chandley et a1... 164/6ox [45] Patented Nov. 10,1970

3,346,309 10/1967 Lyons 164/338 [73] Asslgnee United Aircraft Corporation 3 376 915 4/1968 Ch d1 164 125x East Hartford Connecticut an ey I an H 3,385,346 5/1968 Fleck l64l36lX M 3,401,738 9/1968 Parille 164/353 3,405,220 10/1968 Barrow eta1.. l64/361X 3,417,809 12/1968 Sink 164/127 Primary ExamineF-J. Spencer Overholser r Assistant ExaminerJoh n E. Roethel s41 APPARATUS FOR CASTING DIRECTIONALLY Warm SOLIDIFIED ARTICLES scmm'rwr'wlnlnls- ABSTRACT: Articles in which the crystalline structure is [52] [1.8. CI. 164/338, directionally controlled as, for example, in directionally 164/60, 164/80, 164/348, 164/352, 164/361 solidified or single crystal articles are cast in individual molds [51} lnt.Cl. 822d 27/04, with a mechanism to control the cooling rate and direction B22d 25/00, B22d 15/04 such that orientation of the crystalline structure is precisely [50] Fieidof l64/50,51, 1 controlled. A graphite susceptor surrounds the individual molds and in cooperation with a chill plate provides the necessary control of the cooling rate and direction.

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Q l 341 'l 1' xrrxizx'rus son cxs'rmc DIRECTIONALLY Soumrmn ARTICLES BACKGROUND OF THE INVENTION SUMMARY OF INVENTION A feature of this invention is a casting apparatus by which these articles may be produced singly or in multiples. Another feature is the more 'precise control of the cooling process in the solidification of the alloysor metals being cast thereby to .obtain the desired structure within'the east article.

' One particular feature -is acastingapparatus for the production of aplurality of cast articles simultaneously in which the alloy in the several cast'articles need not be all the same chemical composition and in which both directionally solidified and'single'crystal articles may be produced in different molds in a single casting apparatus.

One featureisa new form ()fSUSCtiPIODfOI' use in performing the casting process.

' BRIEFDESCRIPTION OFTHEDRAWING 7 single crystal articles.

' FIG. 6 isan enlarged view similar toFIGi 4. of a modified :form of mold. i

oescnnriouor THE PREFERREDEMBODIMENT A vacuum chamber 2 has attached thereto, not shown, suitable well-known devicesfor producing a vacuumtherein. The chamber has a base portion 4 and a cover 6 with cooperating,flanges 8.:andI1'0 for securingwthecover in-position. Ajlifting eye 1.2;may, be, used" for removal and positioning of the cover, c

The basef41hasaichilhplate1:4;mountedtherein so that it isverticallymovahle. lnthe arrangement thisis-accomplished by a cooperatingcylinder lfi-and piston18, the latter havinga piston rod 20 on which.theflchill plateis mounted. Asuitable valve 22 controls' the supplyof. actuatingfluidtothe.piston which, as shown, iseffectively a part, of the.;base.; Suitable flexible fluidconnections24. provide for a circulation of cooling fluid through the chill plate.

Above the chillplate is a fixed, supporting ring 26, on which is positioned a susceptor128 in which the molds 40, FIGJS, are I positioned. The, ring isofisuch-a dimension that thechill plate 1. may be moved upward into contact with the bottom of the susceptor. Within the. vacuum chamberis also aheating means such as; the resistance, heating element =32 for -use. in heating 'the chamber. -Also, in.close surrounding relation to the suscep .-tor are a plurality of axially, aligned primary windings 34a, 34b and 34c of induction. coils .used},for heatingthe susceptor. These coilsaresuitably. supportedas bybrackets-36 resting on ring 26 These coils are, individually controlled by separate switches27; FlG.-3, as will become apparent, so that the coils coils and rest on ring 26. This cylinder has a plurality of axially extending openings 38 therethrough which may be closely spaced leaving only thin walls therebetween. The susceptor is preferably graphite and acts as the secondaries for the primary induction coils, Each opening receives a mold 40, the bottom end of which is approximately in the same plane as the bottom of the susceptor. Spacing above this plane may be used to control the thermal gradients in and rate of solidification in the mold. Suitable projecting elements 42 on the walls of the openings 38 limit the downward movement of the mold within the opening.

The openings 38 are preferably cylindrical and the dimension is such as to fit closely the mold positioned therein. Obviously, if a relatively flat mold were to be used it might be desirable to shape the openings more nearly to the mold shape. The axial dimension of the susceptor is selected to be substantially the same as that of the molds to be used.

Each mold is the shell-mold type and the process for making these molds is now well known. In the presentapparatus the mold has an article portion 44 that has a cavity conformingto the shape of the finished article. In the arrangement shown the article is a turbine blade having a shroud 46, an airfoil portion 48 and a root 50. Below this article portion and forming an extensionbeyond the root 50 is a,growth zone 52 in the mold. The bottom of the mold has an end closure 54.

Above the article portion of the mold is an extension 56, preferably cylindrical to receive a slug of the alloy to be cast. The length of the complete mold is preferably substantially the lengthof the opening in the susceptor in which it is positioned. Obviously the volume of the extension 56 is greater than that of the remainder of the mold so that the slug when melted will -fill the remainder of the mold.

' The mold, as above described, is adapted for making directionally solidified columnar grained articles. A similar mold with av bottom modification will serve for single crystal castings also directionally solidified. For this purpose, as

US. Pat. No. 3,494,709.

When the chill plate is moved into operative position in contact with thebottom surface of the mold grain growth starts in the based the cavity and becomes a single crystal in the zigzag portion with the growth proceeding upwardly on substanmaybe sequentially turned off from. the bottom to the top coil tially a horizontal liquid-solid interface until -the alloy is completely solidified.

A modified form of mold is shown in FIG. 6 in which the mold has the articleportion 46a and above this, instead of a cavity for solidified alloy, there is a pouring sprue 58 through which melted alloy, from externally of the mold is introduced to the mold. In this arrangement several molds are all interconnected by a spider typeof pouring sprue for filling a plurality of molds simultaneously. This arrangement is useable, for example, where all the cast articles are formed from the same alloy. I

In use the susceptor with the molds therein is placed in the furnace and heated therein, with the chill plate spaced from the molds until the entire mold has a temperature above the melting point of the alloy and the mold is then filled with melted alloy either by pouring into the mold or molds, FIG. 6, or by thealloy melting from the top cavity and flowing down into the part of the mold in which the casting is formed. With the susceptor and molds above the alloy melting temperature, the alloy will be kept in a molten condition until solidification is started. 1

To accomplish this, the chill plate is moved into contact with the bottom of the susceptor and the bottoms of the mold and .at about the same time the lowermost heating coil is turned off. The chill plate cools the bottom of the molds and begins the upward solidification within the molds. At the same time the chill plate also cools the bottom of the susceptor, and

this takes place at such a rate that the upwardly moving liquidsolid interface between the solidified alloy and the still liquid alloy above it remains substantially horizontal throughout the entire solidification process.

As the interface moves upwardly successive heating coils from the bottom are turned off to allow the susceptor and the molds therein to be cooled to a lower temperature so that solidification may be completed within the mold. With a susceptor of the type shown and described, it is possible to obtain substantially a uniform temperature throughout the entire susceptor and the molds therein during heating of the molds, and to control effectively the rate of upward cooling of the molds and susceptor during solidification of the alloy in the molds. The rate of cooling and thus the rate of alloy solidification is readily controlled by the heat absorption effect of the chill plate and the rate at which the successive heating coils are cut out during the cooling. The rate of cooling may under certain conditions be controlled by withdrawal of the susceptor from within the induction coils rather than by successively cutting out the coils.

I claim:

1. A casting device including a chill plate, a susceptor adapted to rest on the plate during casting and having a plurality of vertically extending openings therethrough, a plurality of vertically spaced heating coils around the susceptor, and a shell-type casting mold positioned in each vertically extending opening, and each mold being a close fit within the openmg.

2. A device as in claim 1 in which each mold has an article forming portion and a growth zone between the article portion and the bottom of the mold.

3. A device as in claim 2 in which the growth zone is a circuitous path for forming a single crystal.

4. A device as in claim 1 in which the susceptor is graphite and the heating coils are individually controlled induction coils.

5. A device as in claim 1 in which each mold includes an article forming portion and an alloy receiving cavity above the article forming portion, said cavity receiving alloy to be melted during the casting process, such that different alloys may be used in the several molds.

6. A device for producing a plurality of castings simultaneously with the crystalline structure of the castings controlled directionally. including a graphite susceptor having a plurality of substantially parallel passages therein, a mold closely fitting in each of said passages and terminating at one end wall of the susceptor, means for heating the susceptor and molds to a high temperature, a chill plate, and means for moving the chill plate into contact with said one end wall of the susceptor and the ends of the molds.

7. A device as in claim 6 in which the heating means includes induction coils surrounding the susceptor.

8. A device as in claim 6 in which each mold has an article forming portion and a growth portion below the article portion in which the desired type ofcrystalline growth is initiatedv 

